Genetics, Evolution & Biodiversity Essay Sample

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AIM: To see if there is a difference in biodiversity between two different ecosystems, and to see which one is best at supporting life

INTRODUCTION: In this experiment I have looked at two different ecosystems at my school.

The first ecosystem was behind the English block. Its up on a hill, higher than any other site in the school grounds. It gets lots of sunlight because its up on a hill, also there are not many trees in the ecosystem so the sunlight can reach the ground to the plants below. The only source of water for the ecosystem is rainwater so in the summer it is very dry and the plants die.

The second ecosystem is down at the bottom of the school field it is behind the bushes by the field and has a river running through it. There are lots of trees and bushes in the area with lots of other plants that have lush green leaves. This ecosystem doesn’t receive a lot of sunlight because the trees catch it before it reaches the ground so only a little light ever does reach the ground. This ecosystem is very low compared to the other area. It gets all the rainwater that runs off the field as it’s on a bit of a slope.

Comparing the two ecosystems I can see that the English block forest gets very dry, with only rainwater to water it, but it does get lots of sun light. So in the summer it looks very dry. Whereas the river ecosystem only gets a little sunlight, but has a lot of water from the river and the rain. So it’s very lush and green. The distance between the two systems is about 1km.

PRELIMINARY WORK: At the start of the experiment I went down to the two ecosystems and done some preliminary work. This consisted of getting 4-meter sticks and laying them randomly in one place on the ground. Then I counted all the plants in the 1-meter square. I did this in both ecosystems. I had to also identify all the plants in the square and list how many there was. Then with all this information I worked out the Biodiversity for the two squares.

Here are my results for the ecosystem behind the English block:

List of plants I counted:

6 wild barley
95 bent grass
185 goose grass
42 ivy
The biodiversity of this quadrat is 2.4.

Here are my results for the river ecosystem:

List of plants counted:

2 cow parsley
3 creeping buttercup
1 bindweed
5 ground elder
7 goose grass
6 common grass
The biodiversity of this quadrat is 5.5

image00.pngA table to show the difference in biodiversity between the two quadrats.


Biodiversity means variety of living things. You can work out an index of biodiversity to compare two ecosystems like I have done in the above section. To do this you have to follow this equation:

D = N (N-1)

+ n (n-1)

N = total number of organisms of all species found

n = total number of organisms of a particular species found

+ = sum of all organisms of a particular species.

By using this equation you can work out the biodiversity index of a certain area. The higher the number, the higher the biodiversity. The lower the number, the lower the biodiversity. Which means there’s lots of plants in the ecosystem or there are many plants in the ecosystem.

RESEARCH: In this section I will find out about the plants that are in the two ecosystems.

IVY: Is a climbing trailing plant, which grows wildly across Europe. Grows in regular garden soil, can live in full sun if given lots of water, also grows well in the shade.

COMMON GRASS: Also known as common reed grass. It is common in North America, and other places. Grows in moist soil and likes marshes.

OAK TREE: _ Found wide in Europe, grows in deep, loamy soil that is moist but not waterlogged. They can be planted in the autumn right through to spring, when new growing starts. Oaks need sunlight and water to survive.

CREEPING BUTTERCUPS: Originally found in Northern England. They need moist, fertile sandy soil in a shaded or semi shaded area to grow, with a good supply of water.

GOOSE GRASS: Found in wasteland, lawns, and fields. It is often seen in compacted soils that border trails and roads. Once goose grass becomes established, annual reifications are likely to occur. It is usually found in full sun and often in poorly drained or compacted soil.

COW PARSLEY: Cow parsley inhabits hedgerows, field edges, and the edges of woods and sometimes-waste ground.

GROUND ELDER:Pernicious weed of cultivated, damp ground. It is normally found in shady edges of forest, garden, and parks.

BINDWEED: Bindweed is a perennial weed that spreads from an extensive rootstock as well as from seed. Field bindweed tolerates a great range of environmental conditions and elevations and is found in all types of ground, including cultivated fields and waste places. It grows best on fertile, dry or moderately moist soils and is extremely difficult to control.

PREDICTION: I predict that the difference in the biodiversity between the two ecosystems will be very large. I predict this because when I look at the biodiversity scores I got on the preliminary quadrats, there is a big difference in the two scores. The forest quadrat had a biodiversity score of 2.4, whereas the river quadrat had a score of 5.5. The difference between them is 3.1. There were more plants in the river quadrat then the forest quadrat, so this makes a difference right away. The forest doesn’t get a lot of water so it can’t support much plant life whereas the river has lots of water because it has a river in it. The river is also more shaded and doesn’t get direct sun light unlike the forest so this also plays a part in why I think there will be a big difference in the ecosystems.

INFORMATION I HAVE COLLECTED: In the test I collected a lot of information. This was divided into two groups, which were abiotic factors, and biotic factors. Abiotic factors are the non-living things, which affect an ecosystem. Biotic factors are the living organisms in the ecosystem.

The abiotic factors were:

Light intensity
Temperature of soil
PH of soil
Water content of soil
The biotic factors were:

The plants (quadrat counts)
METHODS I USED: To collect the above information I used lots of different methods:

Light intensity: To collect this information I used a piece of equipment called a datalogger, which had a light senor connected to it. The light sensor measures the amount of light that is in an area. I measured the light intensity in each of my quadrats.
Temperature of Soil: To collect this information I put a thermometer in the ground where each of my quadrats were, left it a few minutes then took down its readings

PH of Soil: I collected this by taking four samples of soil from the same ecosystem, mixing them in the same bag. Then I put some of the soil into 5 boiling tubes, added some water, then I added some universal indicator into the boiling tubes, then I recorded the PH by looking at the colour of the indicator and comparing the colour to a chart of PHs. I done this for both ecosystems.

Water Content of Soil: To collect this I used the same soil I got from the PH test. I got a tin lid put in on some scales and weighed it. I recorded this weight. Then I added some soil to the tin lid. Weighed it again. Then I placed to over a Bunsen burner for 5 minutes to burn off the water in the soil. After the 5 minutes I put tin back on the scales and weighed it again. With this weight I had to subtract the weight of the tin from the overall weight. With the left over I subtracted it from the weight before I put it over the Bunsen burner. After this I had the water content of the soil. I done this 5 times for both ecosystems.

The Quadrats: This was when I randomly selected an area of the ecosystem and put down the four meter sticks and counted every plant in the square. Recording how many there were of each plant. I done this in both ecosystems. With 9 quadrats.
THE DATALOGGER AND HOW TO USE IT: This is how to set up and use the datalogger with light sensor.

Connect the TI-83 calculator and the CBL unit together using the TI-83 link cable
Connect the light senor to channel 1 on the CBL unit
Turn on the calculator
Press PRGM on the calculator
Select CHEMBIO using arrows, when found press ENTER
Press ENTER two more times

Press 1 for number of probes, press ENTER
Select LIGHT, press ENTER
Press 1 for channel number, press ENTER
Place light sensor on the ground with the sensor side facing directly towards the sky
Read the value off the CBL and record it.
RESULTS: Here are all my results that I got from my tests in the above methods. I have put them into two sections; these are The Forest Ecosystem and The River Ecosystem.

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